<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Title</title>
  <style>
    * {
      margin: 0;
      padding: 0;
    }

    .search {
      position: relative;
      width: 178px;
      margin: 100px;
    }

    .con {
      display: none;
      position: absolute;
      top: -40px;
      width: 171px;
      border: 1px solid rgba(0, 0, 0, .2);
      box-shadow: 0 2px 4px rgba(0, 0, 0, .2);
      padding: 5px 0;
      font-size: 18px;
      line-height: 20px;
      color: #333;
    }

    .con::before {
      content: '';
      width: 0;
      height: 0;
      position: absolute;
      top: 28px;
      left: 18px;
      border: 8px solid #000;
      border-style: solid dashed dashed;
      border-color: #fff transparent transparent;
    }
  </style>
</head>
<body>
<div class="search">
  <div class="con">123</div>
  <input type="text"/>
</div>
<script>
  var con = document.querySelector('.con');
  var input = document.querySelector('input');
  document.addEventListener('keyup', function () {
    if (input.value === '') {
      con.style.display = 'none';
    } else {
      con.innerHTML = input.value;
      con.style.display = 'block';
    }
  })
  input.addEventListener('blur', function () {
    con.style.display = 'none';
  })
</script>
</body>
</html>